Meinberg GEN170TGP - Manual (Page 7)

7
GEN170
GEN170 Overview
The time code generator GEN170 has been
designed to generate all signals required to control or
simulate a DCF77 compatible long wave transmitter,
or provide the reference time for an NTP server:
o 77.5 kHz carrier frequency
o second marks to modulate the carrier's
amplitude
o PRN sequence and PRN window to modulate
the carrier's phase
o Pulse-per-Second (PPS) output
Additionally, an IRIG or AFNOR time code signal is generated, and a serial time
string can be transmitted which includes the generated absolute date and time.
All signals are derived from a single 10 MHz reference frequency. That frequency can
either be generated by a high quality on-board oscillator, or it can be supplied externally.
The frequency source is selected by a jumper on the printed circuit board. The leading
edge of the second marks can be synchronized by an external PPS input signal.
Internal date and time is always based on UTC (Universal Time, Coordinated;
formerly GMT, Greenwich Mean Time). A configurable time offset can be applied to the
UTC time base to compute a local standard time. Beginning and end of a period of
daylight saving time can either be computed year by year based on a simple, configurable
algorithm, or can be configured for the current year. GEN170 generates the proper
changeover announcement flags as required by the DCF77 coding scheme.
Additionally, a date for insertion of a leap second can be configured. Actually, leap
seconds are only inserted at UTC midnight. GEN170 automatically generates the coding
sequences to announce the leap second as required for DCF77 and NTP, and also inserts
the leap second correctly.
16 TTL level inputs are provided to configure the length of the AM marks transmitted
in seconds 0 through 15 of a minute in DCF77 emulation. These second marks are
reserved by the PTB and are igno*red by most DCF77 receivers.
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